In conventional cooling arrangements, in which circuit packs are edge mounted in a circuit pack cage and plugged into a so-called backplane wiring board attached to the cage, a cooling gas enters the bottom of the cabinet, rises vertically and passes over the heat generating components mounted on the circuit packs and then exits via louvers formed in the top surface of the cabinet. The vertical flow of the cooling gas is augmented by a forced convection system, such as a blower fan placed at the bottom of the cabinet or just beneath the circuit packs. Although such cooling arrangements are adequate, they are still faulty in some notable respects. For exmaple, when a blower fan is placed in proximity to the circuit packs, the flow of the cooling gas forms a vortex, thereby causing uneven cooling of the heat generating components. In addition, when the circuit packs are of different lengths, pockets of cooling gas formed by face plates attached to one end of the longer circuit packs prevent the cooling gas from flowing evenly over components mounted at the front of the circuit packs.
Alternatively, the circuit pack cage could be rotated 90 degrees so that it is mounted vertically in the cabinet. The cooling gas could then enter one side of the cabinet, flow over the heat generating components and exit via the opposite side of the cabinet. However, such a cooling arrangement would be ineffective in the instance where it is contemplated that at least two such cabinets will be placed side-by-side, since one cabinet would exhaust heated cooling gas into the next adjacent cabinet. With the circuit pack cage so oriented, the cooling gas could be arranged, on the other hand, so that it enters the front surface of the cabinet, flows over the heat generating components and then exits via the rear surface of the cabinet. However, in this instance, the backplane would impede the flow of the cooling gas causing it to form a turbulence within the cabinet.